Synchronous powder-feeding space laser machining and three-dimensional forming method and device

ABSTRACT

A method for synchronous powder-feeding space laser cladding and three-dimensional forming includes: dividing a three-dimensional solid into a plurality of forming units according to a form simplification and nozzle cladding scanning accessibility principle, and dividing each forming unit into a plurality of layers; employing a single-beam gas-carried power-feeding mode in a hollow annular laser; controlling a mechanical arm ( 7 ) to drive an in-laser powder-feeding nozzle ( 1 ) to move and scan along a predetermined trajectory in a filling area and a boundary area of the layer; and sequentially conducting cladding and stacking formation of the layer for the entire unit. A device includes an inside-laser powder-feeding nozzle ( 1 ), a laser generator ( 6 ), a mechanical arm ( 7 ), a control module ( 4 ), a transmission optical fiber ( 5 ), a gas-carried powder feeder ( 3 ) and a gas source ( 2 ).

TECHNICAL FIELD

The present invention relates to a laser processing forming technology,particularly to a method and device for synchronous powder-feeding spacelaser cladding and three-dimensional forming.

BACKGROUND TECHNOLOGY

The additive manufacturing technology is a technology that manufacturesa solid part by gradually adding materials. There are two common laseradditive manufacturing methods for metal, laser powder-bed selectivesintering melting and laser synchronous material-feeding claddingforming. The selective sintering method, using a powder bed as asupport, can form a metal part having complex shape and an overhang, butsuffers from expensive equipment, a high cost, and limited forming size.Cladding forming metal by the laser synchronous material-feeding methodcan approach or achieve performance of forgings at a low cost, and canbe integrated with various CNC machine tools, mobile robots and so on tofreely form a large three-dimensional solid; it can clad the surface ofan important part with a high-performance alloy layer, doubling the lifeor giving the part special function; it can repair and remanufacture thedamaged portion of a part to get the part back to life; it can flexiblycomplete urgent repair, urgent rescue and other operations on equipmentat a fixed location, the project site or the war frontline. The lasersynchronous material-feeding cladding processing forming has become anadvanced and even indispensable processing forming means in many areas.

In the prior art, the synchronous powder-feeding laser three-dimensionalforming has the following steps: First slicing the computerthree-dimensional model to be formed into a solid with a series ofhorizontal planes to get a two-dimensional sectional model of a numberof layers; then a laser beam and metal powder sent out of a laser-powdercoupling nozzle are focused and converged on the forming surfacesimultaneously, with the focused laser spot irradiated onto the powderspot to make it quickly molten together with the superficial layer ofthe base surface to form a molten pool; with the laser-powder couplingnozzle scanning along a predetermined path, the molten pool rapidlysolidifies into a solid molten channel; thus, by scanning and formingaccording to the shape of each layer, the laser-powder coupling nozzlerises vertically by a height of one layer each time one layer of solidis formed, and then a next layer starts to be scanned and formed; andfinally the layers are stacked and accumulated to produce athree-dimensional solid. The essence of this method is dimensionalityreduction; that is, a three-dimensional solid is sliced into multiplehorizontal parallel two-dimensional layers, and then all the horizontallayers are stacked vertically in turn to accumulate into athree-dimensional solid, which is called the “vertical growth method”. Abasic requirement of the three-dimensional forming is that, when thelaser-powder coupling nozzle is scanning along any direction within atwo-dimensional layer, the laser and the powder are coaxial to keeptheir coupling pose unchanged, so as to get an isotropic molten channel;therefore, in order to keep the scanning isotropy, a coaxialpowder-feeding method is generally used for stacking accumulating layersfor three-dimensional forming. There are two coaxial powder-feedingmethods: A coaxial powder-feeding nozzle as disclosed in a U.S. patent(U.S. Pat. No. 5,418,350; U.S. Pat. No. 5,477,026; U.S. Pat. No.5,961,862), a European patent (WO2005028151), a Japanese patent(JP2005219060) and other patents has the following basic structure: anannular or multi-channel powder-feeding tube is arranged slantwisearound a solid focused laser beam 22, and converges the outputted powderbeam 23 in the focused laser spot formed by the laser beam on theforming base surface, which can be called the “outside-laserpowder-feeding method”, as shown in FIG. 1. The outside-laserpowder-feeding method, converging multi-channel powder beam, hasdivergent powder, a coarse powder spot, only one point of convergence,and a narrow range in which the laser beam can be coupled, makingcoupling not easy to be done. Another method is an inside-laserpowder-feeding nozzle disclosed in the patent CN2006101164131 and otherpatents, which converts the laser beam 22 into a hollow annular focusedlaser beam, and then sends a single powder beam 23 coaxially within theannular laser beam perpendicularly to the inside of the focused laserspot on the forming surface, as shown in FIG. 2. The inside-laserpowder-feeding method uses a single powder beam, with the powder beamlong and thin and the powder spot small; since the laser and the powderare really coaxial, the laser-powder coupling range is wide, makingcoupling easy to be done. In particular, when a protective gas tube issleeved outside the powder-feeding spray tube, an annular gas curtain isformed at the periphery of the powder beam, and can play a further rolein clustering and collimating the powder beam.

It can be seen from the existing synchronous powder-feedingthree-dimensional forming method that, this method allows no-supportfree forming, and can only use the cladded molten channel in the lowerlayer as the support for the upper layer in the horizontal layeredaccumulation; when forming an overhang or a cavity structural part, theupper layer will be displaced partially relative to the lower layer toresult in the “step effect” on the surface; when there is excessive orcomplete dislocation, light-powder leakage and molten pool flow will becaused, and even forming cannot be carried out, as shown in FIG. 3.Under the action of a tension of the molten pool, the small dislocationbetween the upper and lower layers can still allow a small-angleinclined wall structure to be formed, but cannot allow a big-angleinclined part, an overhang or a cavity and other similar structuralparts to be formed. Therefore, currently the synchronous powder-feedinglaser three-dimensional forming can be generally only used for thecladding reinforcement and repair in the horizontal plane and thehorizontally layered three-dimensional forming, but still cannot be usedfor the cladding reinforcement and repair on a facade, an incline, abottom surface or any other surface in the space and the space-layeredthree-dimensional forming. A literature (Luo Tao, Yang Xichen, LiuYunwu, et al., Three-dimensional laser coaxial powder-feeding system andindustrial application thereof, Manufacturing Technology and Equipment,2005(2): 121-123) discloses a coaxial powder-feeding system with sixdegrees of freedom, allowing a nozzle to oscillate within a certaininclination; a literature (Wu X, Mei J., Near net shape manufacture ofcomponents using direct laser fabrication technology, Journal ofMaterials Processing Technology, 2003, 135(2-3): 266-270) uses the lasersynchronous powder-feeding process to manufacture a characteristicstructure having an inclination smaller than 30°, but still cannotmanufacture a structure having a big inclination. A U.S. patentUS2012/0100313A1 reports an upright cylindrical surface laser claddingmethod, by which the powder beam is sprayed slantwise upward from a sideof the laser beam, the molten pool is supported by an upward componentforce of the powder and gas stream, and then the cylinder is rotated andthe nozzle moves relative to the busline to get the facade cladded. Thismethod of feeding powder from a side of the laser, not coaxially feedingthe powder, is only applicable to cladding in a fixed direction, butcannot meet the requirements of facade forming for isotropy, not tomention the three-dimensional forming on any surface in the space.

Currently the synchronous powder-feeding laser three-dimensionalcladding and forming method has the following shortcomings: (1) In thelayered three-dimensional forming of an overhanging structural part,forming dislocation is caused at the upper and lower layers at theoverhanging boundary because of no support, which will reduce theforming accuracy on the less serious occasion to result in the “stepeffect” on the surface, and will cause laser-powder leakage and moltenpool flow on the serious occasion to make accumulating forming notsustainable; (2) it can only form an upright structure or a less outwardinclined structure and other simple structures, but cannot form agreatly outward inclined structure, a cantilever or a cavity and othercomplex structures; and (3) it can only allow cladding process, repairor forming of a horizontal plane or a small-angle incline, but cannotallow cladding process, repair or three-dimensional accumulating formingon any inclines in the space. Therefore, a new method and device forsynchronous powder-feeding space laser cladding and three-dimensionalforming is needed, which can carry out cladding process and stereoscopicaccumulating forming on any inclines in the space, and can form agreatly outward inclined structure, a cantilever, a cavity and othercomplex parts by three-dimensional forming that allows changingdirection and pose in the space continuously.

SUMMARY OF THE INVENTION

A purpose of the present invention is to provide a method and device forsynchronous powder-feeding laser three-dimensional forming, which cancarry out cladding process and stereoscopic accumulating forming on anysurface in the space, and can carry out no-support three-dimensionalforming of an overhang, a cavity and other complex parts.

In order to achieve the above purpose, the present invention adopts thefollowing technical solution: A method for synchronous powder-feedingspace laser cladding and three-dimensional forming is provided,comprising the following steps:

(1) Dividing a multi-branch complex three-dimensional solid expected tobe formed into at least one forming unit based on the principle of bodysimplification and nozzle cladding scanning accessibility, and selectingthe forming sequence of each unit in turn, with each forming unit havinga respective optimal forming growth direction and rule;

(2) dividing the forming unit obtained in the step (1) into a number oflayers in the stacking accumulating direction, each layer including atleast one of a filling region and a boundary region;

(3) using the hollow annular laser inside-laser single-beam gas-carriedpowder-feeding method to control a mechanical arm to drive aninside-laser powder-feeding nozzle to scan and move in the boundaryregion and the filling region of a layer along a predetermined track, soas to complete cladding, accumulating and forming of this layer,respectively; in scanning forming, the laser-powder spray axis of theinside-laser powder-feeding nozzle is always along the normal directionof the layer; when the filling region and the boundary region areinconsistent in the layering direction, i.e., the layers are notparallel to each other, the nozzle needs to be deflected to completecladding forming of different regions, respectively;

(4) after cladding forming of a layer, the nozzle retreats by a distanceof thickness of one layer along the growth direction of a next layer,and completes scanning cladding forming of a new layer according to thestep (3); repeating in this way, until the stacking accumulation of theentire forming unit is completed; wherein the nozzle needs tocontinuously change its position for each layer in forming the boundaryof a curved surface, with the stacking forming always done along thebending direction of the boundary; and

(5) after completing a forming unit, controlling the mechanical arm tomove the inside-laser powder-feeding nozzle to the start position of anext forming unit, so as to repeat the steps (2), (3) and (4) forstacking accumulating forming of a new forming unit; repeating in thisway, until completing all the unit accumulation of the entirethree-dimensional solid.

In the step (2) of the above technical solution, all the layers in thefilling region, parallel to each other, are parallel to the basesurface; when the boundary region is layered, it is sliced along thevertical direction of the boundary face; when the boundary face isstraight faced, the layers are parallel to each other and equal inthickness; when the boundary face is a curved surface, the layers areneither parallel to each other nor equal in thickness.

A device for synchronous powder-feeding space laser cladding andthree-dimensional forming is provided, comprising an inside-laserpowder-feeding nozzle, a laser generator, a mechanical arm, a controlmodule, a transmission fiber, a gas-carried powder feeder and a gassource; the control module is connected with the mechanical arm, thelaser generator, and the gas-carried powder feeder, respectively, theinside-laser powder-feeding nozzle is fixed at the front end of themechanical arm, and the laser output of the laser generator is connectedvia the transmission fiber to the upper end of the inside-laserpowder-feeding nozzle; a gas-supplying branch of the gas source is incommunication with the gas-carried powder feeder, which is incommunication with a powder spray tube in the inside-laserpowder-feeding nozzle, with a collimating gas tube sleeved outside thepowder spray tube; another gas-supplying branch of the gas source is incommunication via a tube with the collimating gas tube in theinside-laser powder-feeding nozzle.

In the above technical solution, the pressure of the gas-carried powdersprayed out of the powder spray tube can be adjusted to 0-0.2 Mpa.

In the above technical solution, the pressure of the annular collimatinggas sprayed out of the collimating gas tube can be adjusted to 0.05-0.3Mpa.

In the above technical solution, the ratio of the diameters of thepowder spray tube and the collimating gas tube is 1:2-1:6.

In the above technical solution, the outlet of the powder spray tubeextends beyond the outlet of the collimating gas tube by a length of0-20 mm.

In the above technical solution, the gas outputted from the gas sourceis an inert gas.

With the above technical solution, the present invention has thefollowing advantages compared with the prior art:

1. The present invention uses the hollow laser inside-laser single-beampowder-feeding method, with the track of the powder beam simple and easyto be controlled; with the gas-carried powder-feeding method, when theaxis of the inside-laser powder-feeding nozzle is located in any angularposition in the space, adjusting the pressure of the gas-carried powderand the pressure of the annular collimating gas in a matching way tobalance the influence of gravity, so as to make the single powder beamthin, erect, collimating, and straight within a certain range, such thatthe laser and powder can be coupled accurately on the forming surface toallow the powder to be fed to the molten pool accurately. The presentinvention, under the condition that the axis of the inside-laserpowder-feeding nozzle is located at any angle in the space, makes thelaser beam, the gas-carried powder beam and the annular collimating gascompletely coaxial, and uses the appropriate structure and size of apowder gas tube, the appropriate carried powder and annular collimatinggas pressure, and the appropriate cladding process parameters; inspatial forming, both the gas-carried powder and the annular collimatinggas have a forward pressure that presses the molten pool onto theforming surface, guaranteeing that the molten pool will not flow whilesolidifying, such that a stable molten channel can be formed on anyangular base surface in the space.

2. The present invention uses a space zoning planned forming unit forthe laser three-dimensional forming part, wherein each unit can besubject to different layering method and planning, the layers can beparallel or nonparallel to each other and can be equal or unequal inthickness, and the boundary layer and the filling layer of each layercan have different accumulating forming direction. Therefore, thepresent invention can not only complete cladding reinforcement or repairof any inclined surface in the space, but also break the limit of thetraditional synchronous material-feeding laser three-dimensional formingprocess that a simple solid can be formed only by slicing with ahorizontal plane and forming from bottom to top, allowing claddingforming and layered accumulation along different inclination directionin the space, allowing three-dimensional forming of parts containing acantilever, a cavity and other complex structures by processing formingand continuously changing direction on any inclined base surface.

3. The present invention, for a three-dimensional solid with a slantwiseoverhanging surface, uses a boundary zone method for layering theboundary, i.e. always slicing perpendicularly to the overhangingslantwise boundary; in stacking accumulating forming, the laser-powderspray axis is always placed in the tangential direction of the outersurface of the forming unit, with the upper and lower layers basicallyall covered without dislocation, which can remove the “step effect”,improve the forming accuracy and reduce the surface roughness; inlayering, the thickness of the layer can also be appropriatelyincreased, so as to improve the forming efficiency while achieving asmoothly formed surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an existing outside-laserpowder-feeding nozzle in the background of the invention.

FIG. 2 is a schematic diagram of an existing inside-laser powder-feedingnozzle in the background of the invention.

FIG. 3 is a schematic diagram of the horizontal layered dislocation ofthe existing curved boundary in the background of the invention.

FIG. 4 is a schematic diagram of the connection of the device forsynchronous powder-feeding space laser cladding and three-dimensionalforming of the present invention in Example 1.

FIG. 5 is a diagram of the relation between the powder spray tube andthe collimating gas tube of the present invention in Example 1.

FIG. 6 is a schematic diagram of the method for forming unit by unit amulti-branch structural part of the present invention in Example 2.

FIG. 7 is a schematic diagram of the unit zoning forming method of thepresent invention in Example 3.

FIG. 8 is a schematic diagram of the normal layering forming method ofthe curved boundary of the present invention in Example 3.

FIG. 9 is a schematic diagram of the solid forming method of themultiple boundary regions of the present invention in Example 4.

FIG. 10 is a schematic diagram of the solid forming method of theboundary face with the same degree of curvature of the present inventionin Example 5.

FIG. 11 is a schematic diagram of the method for forming a thin-walledrotating part of the present invention in Example 6.

FIG. 12 is a schematic diagram of the method for repairing defects onthe base surface with any inclination of the present invention inExample 7.

List of reference signs: 1. An inside-laser powder-feeding nozzle; 2. agas source; 3. a gas-carried powder feeder; 4. a control module; 5. atransmission fiber; 6. a laser generator; 7. a mechanical arm; 8. aforming part; 9. a powder spray tube; 10. a collimating gas tube; 11. aforming unit a; 12. a forming unit b; 13. a forming unit c; 14.gas-carried powder; 15. annular collimating gas; 16. a filling region;17. a boundary face; 18. a boundary region; 19. a base surface; 20. arotary table; 21. a surface to be repaired; 22. a laser beam; and 23. apowder beam.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be further described below with reference todrawings and examples.

EXAMPLE 1

A method for synchronous powder-feeding space laser cladding andthree-dimensional forming is provided, comprising the following steps:

(1) Dividing a multi-branch complex three-dimensional solid expected tobe formed into one or more forming units based on the bodysimplification and nozzle cladding scanning accessibility principle, andselecting the forming sequence of each unit in turn, with each formingunit having a respective optimal forming growth direction and rule;

(2) dividing the forming unit obtained in the step (1) into a number oflayers along the stacking accumulating direction, each layer at leastincluding one of the filling region and the boundary region;

(3) using a hollow annular laser inside-laser single-beam gas-carriedpowder-feeding method to control a mechanical arm to drive aninside-laser powder-feeding nozzle to scan and move in the boundaryregion and the filling region of a layer along a predetermined track, soas to complete cladding accumulating forming of this layer,respectively; in scanning forming, the laser-powder spray axis of theinside-laser powder-feeding nozzle is always along the normal directionof the layer; when the filling region and the boundary region areinconsistent in the slicing direction, i.e., the layers are not parallelto each other, the nozzle may need to be deflected to complete claddingforming of the different regions, respectively;

(4) after cladding forming of a layer, the nozzle can retreat by adistance of thickness of one layer along the growth direction of a nextlayer, and completes scanning cladding forming of a new layer accordingto the step (3); the nozzle needs to get its position continuouslychanged in forming the boundary region of each layer, stacking formingalways along the bending direction of the boundary, with the upper andlower layers all covered without dislocation, avoiding the laser-powderleakage caused by a stacking fault, removing the “step effect”;repeating in this way, until the stacking accumulation of the entireforming unit is completed; and

(5) after completing a forming unit, controlling the mechanical arm tomove the inside-laser powder-feeding nozzle to the start position of anext forming unit, so as to repeat the steps (2), (3) and (4) forstacking accumulating forming of a new forming unit; repeating in thisway, until completing all the unit accumulation of the entirethree-dimensional solid.

In this example, the layering principle of the boundary region is asfollows: Slicing along the vertical direction, i.e. the normal directionof the boundary face. When the boundary face is straight faced, thelayers are parallel to each other and equal in thickness; when theboundary face is a curved surface, the layers can be neither parallel toeach other nor equal in thickness. The layering principle of the fillingregion is as follows: The layers are all parallel to the base surfaceand also parallel to each other.

As shown in FIGS. 4 and 5, a device for synchronous powder-feeding spacelaser cladding and three-dimensional forming is provided, comprising aninside-laser powder-feeding nozzle 1, a laser generator 6, a mechanicalarm 7, a control module 4, a transmission fiber 5, a gas-carried powderfeeder 3 and a gas source 2; the control module 4 is connected with themechanical arm 7, the laser generator 6 and the gas-carried powderfeeder 3, respectively, and controls movement of the mechanical arm 7;the inside-laser powder-feeding nozzle 1 is fixed at the front end ofthe mechanical arm 7, and can move in the space with the mechanical arm7, so as to form on any angular base surface in the space andcontinuously change position and pose for cladding forming according tothe path plan given by the control module 4, thus producing a formingpart 8. The laser output of the laser generator 6 is connected via thetransmission fiber 5 to the upper end of the inside-laser powder-feedingnozzle 1; a gas-supplying branch of the gas source 2 is in communicationwith the gas-carried powder feeder 3, which is in communication with apowder spray tube 9 in the inside-laser powder-feeding nozzle 1, so asto transport the gas-carried powder 14; with a collimating gas tube 10sleeved outside the powder spray tube 9, another gas-supplying branch ofthe gas source 2 is in communication via a tube with the collimating gastube 10 for transporting the annular collimating gas 15.

In this example, the pressure of the gas-carried powder 14 sprayed outof the powder spray tube 9 can be adjusted to 0-0.2 Mpa, the pressure ofthe annular collimating gas 15 sprayed out of the collimating gas tube10 can be adjusted to 0.05-0.3 Mpa, the ratio of the diameters of thepowder spray tube 9 and the collimating gas tube 10 is 1:2-1:6, theoutlet of the powder spray tube 9 extends beyond the outlet of thecollimating gas tube 10 by a length of 0-20 mm, and the gas outputtedfrom the gas source 2 is an inert gas.

EXAMPLE 2

As shown in FIG. 6, dividing the three-branch three-dimensional forminginto three simple-shaped forming units a, b and c according to the bodysimplification and inside-laser powder-feeding nozzle accessibilityprinciple; wherein the forming unit a11 has a forming growth directiona1, the forming unit b12 has a forming growth direction b1, and theforming unit c13 has a forming growth direction c1. The forming sequenceis as follows: First forming the forming unit a11, then controlling themechanical arm 7 to move the inside-laser powder-feeding nozzle 1 to thestart position of the forming unit b12 to form the forming unit b12 onthe sidewall of the forming unit a11, and then controlling themechanical arm 7 to move the inside-laser powder-feeding nozzle to thestart position of the forming unit c13 to form the forming unit c13 onthe other side of the forming unit a11, and so on, until completing theunit accumulation of the entire three-branch three-dimensional solid.

EXAMPLE 3

The synchronous powder-feeding space laser cladding andthree-dimensional forming of the curved overhanging structural part isshown in FIGS. 7 and 8, which uses a zoning method, dividing the formingunit along the optimal growth accumulation direction into a number oflayers, with each layer divided into a boundary region 18 and a fillingregion 16. The layering principle of the boundary region 18 is asfollows: Always slicing along a direction perpendicular to the boundaryface 17, i.e. along the normal direction of the boundary face; when theboundary face is straight faced, the layers are parallel to each other;when the boundary face is a curved surface, the layers can be neitherparallel to each other nor equal in thickness. The layering principle ofthe filling region 16 is as follows: All the layers are parallel to thebase surface 19 and also parallel to each other. After cladding forminga layer, the nozzle retreats by a distance of thickness of one layeralong the growth direction of the layers, so as to complete scanningcladding forming of a new layer. Repeating in this way, until thestacking accumulation of the entire forming unit is completed. For thecurved boundary region 18, the position of the nozzle needs to becontinuously changed for forming each layer, and stacking forming iscarried out always along the normal direction of the boundary. Thezoning forming method can make the upper and lower layers entirelycovered without dislocation, avoid the laser-powder leakage caused by astacking fault, and remove the “step effect”.

EXAMPLE 4

In Example 3 as shown in FIG. 9, the forming unit can include one ormore boundary faces 17, i.e. including one or more boundary regions 18.

EXAMPLE 5

As shown in FIG. 10, when multiple boundary faces 17 of the forming unitare parallel to each other or have the same degree of curvature, thefilling region 16 can be consistent with the boundary region 18 in thelayering direction, that is, both the filling region 16 and the boundaryregion 18 are based on the layering principle of always layering along adirection perpendicular to the boundary face 17, i.e. along the normaldirection of the boundary face.

EXAMPLE 6

As shown in FIG. 11, for the synchronous powder-feeding space lasercladding and three-dimensional forming of the thin-walled rotating part,the part is only divided into the boundary region 18 according tocharacteristics of the thin-walled structure, layered along the verticaldirection of the curved boundary face 17. Controlling the mechanical arm7 to retain the inside-laser powder-feeding nozzle 1 to the normaldirection of the boundary face for cladding forming, meanwhile drivingthe base surface 19 to rotate by the rotary table 20 by accumulating onelayer per revolution, and then controlling the mechanical arm 7 alongthe predetermined track to retain the inside-laser powder-feeding nozzle1 to retreat by a distance of thickness of one layer for accumulating anext layer, until the stacking accumulation of the entire thin-walledrotating part is completed.

EXAMPLE 7

As shown in FIG. 12, for the space laser cladding and three-dimensionalforming repair method for the damaged parts on the base surface with anyinclination, layering the filling region 16 by taking the damaged partof the surface 21 to be repaired as the filling region 16, with all thelayers parallel to the surface 60 to be repaired. Controlling themechanical arm 7 to retain the inside-laser powder-feeding nozzle 1 tocomplete cladding forming of a layer, and then controlling themechanical arm 7 along the predetermined track to retain theinside-laser powder-feeding nozzle 1 to retreat by a distance ofthickness of one layer for accumulating a next layer, until completingstacking filling accumulating repairing forming of the entire damagedpart.

What is claimed is:
 1. A method for synchronous powder-feeding spacelaser cladding and three-dimensional forming, comprising the followingsteps: (1) dividing a multi-branch complex three-dimensional solidexpected to be formed into at least one forming unit based on theprinciple of body simplification and nozzle cladding scanningaccessibility, and selecting the forming sequence of each unit in turn,with each forming unit having a respective optimal forming growthdirection and rule; (2) dividing the forming unit obtained in the step(1) into a number of layers in the stacking accumulating direction, eachlayer including at least one of a filling region and a boundary region;(3) using the hollow annular laser inside-laser single-beam gas-carriedpowder-feeding method to control a mechanical arm to drive aninside-laser powder-feeding nozzle to scan and move in the boundaryregion and the filling region of a layer along a predetermined track, soas to complete cladding, accumulating and forming of this layer,respectively; in scanning forming, the laser-powder spray axis of theinside-laser powder-feeding nozzle is always along the normal directionof the layer; when the filling region and the boundary region areinconsistent in the layering direction, i.e., the layers are notparallel to each other, the nozzle needs to be deflected to completecladding forming of different regions, respectively; (4) after claddingforming of a layer, the nozzle retreats by a distance of thickness ofone layer along the growth direction of a next layer, and completesscanning cladding forming of a new layer according to the step (3);repeating in this way, until the stacking accumulation of the entireforming unit is completed; wherein the nozzle needs to continuouslychange its position for each layer in forming the boundary of a curvedsurface, with the stacking forming always done along the bendingdirection of the boundary; and (5) after completing a forming unit,controlling the mechanical arm to move the inside-laser powder-feedingnozzle to the start position of a next forming unit, so as to repeat thesteps (2), (3) and (4) for stacking accumulating forming of a newforming unit; repeating in this way, until completing all the unitaccumulation of the entire three-dimensional solid.
 2. The method forsynchronous powder-feeding space laser cladding and three-dimensionalforming according to claim 1, wherein in step (2), all the layers in thefilling region, parallel to each other, are parallel to the basesurface; when the boundary region is layered, it is sliced along thevertical direction of the boundary face; when the boundary face isstraight faced, the layers are parallel to each other and equal inthickness; when the boundary face is a curved surface, the layers areneither parallel to each other nor equal in thickness.
 3. A device forsynchronous powder-feeding space laser cladding and three-dimensionalforming, which characterized in, comprising an inside-laserpowder-feeding nozzle, a laser generator, a mechanical arm, a controlmodule, a transmission fiber, a gas-carried powder feeder and a gassource; the control module is connected with the mechanical arm, thelaser generator, and the gas-carried powder feeder, respectively, theinside-laser powder-feeding nozzle is fixed at the front end of themechanical arm, and the laser output of the laser generator is connectedvia the transmission fiber to the upper end of the inside-laserpowder-feeding nozzle; a gas-supplying branch of the gas source is incommunication with the gas-carried powder feeder, which is incommunication with a powder spray tube in the inside-laserpowder-feeding nozzle, with a collimating gas tube sleeved outside thepowder spray tube; another gas-supplying branch of the gas source is incommunication via a tube with the collimating gas tube in theinside-laser powder-feeding nozzle.
 4. The device for synchronouspowder-feeding space laser cladding and three-dimensional formingaccording to claim 3, wherein the pressure of the gas-carried powdersprayed out of the powder spray tube is between 0 to 0.2 Mpa.
 5. Thedevice for synchronous powder-feeding space laser cladding andthree-dimensional forming according to claim 3, wherein the pressure ofthe annular collimating gas sprayed out of the collimating gas tube isbetween 0.05 to 0.3 Mpa.
 6. The device for synchronous powder-feedingspace laser cladding and three-dimensional forming according to claim 3,wherein the ratio of the diameters of the powder spray tube and thecollimating gas tube is 1:2 to 1:6.
 7. The device for synchronouspowder-feeding space laser cladding and three-dimensional formingaccording to claim 3, wherein the outlet of the powder spray tubeextends beyond the outlet of the collimating gas tube by a length of 0to 20 mm.
 8. The device for synchronous powder-feeding space lasercladding and three-dimensional forming according to claim 3, wherein thegas outputted from the gas source is an inert gas.